Studies in the pediatric intensive care unit (PICU) have shown that hypoglycemia, hyperglycemia as well as swings in blood glucose levels are strongly associated with higher morbidity and mortality. However, tight glucose control has not been proven as effective. In fact, hypoglycemia was found to be a real danger. Thus, there is a need for more careful study, collection of more data using standardized methods over a larger cohort in the PICU. However, multiple painful blood withdrawals or an indwelling needle cause additional stress to both the young patients in the PICU, their parents and caregivers. Here we propose to develop a painless, minimally invasive glucose sensing system designed especially for patients in the PICU. Microneedles (MNs, between 250 to 750m in length), will be used to create microchannels in the outer layer of dead cells (corneocytes) on the skin. A small biosensor patch containing a highly sensitive (Kd ~ M) optical glucose biosensor will be placed over these microchannels to allow glucose to diffuse. The rate of diffusion of glucose will then be measured using a handheld minifluorometer. The device will be tested and optimized in vitro on model skin and on selected healthy subjects and patients in the PICU.